1. Technical Field
One or more embodiments of the invention generally relate to methods, systems, and apparatuses for producing infrared (IR) detectors in volume quantities, and more particularly, for the wafer level packaging (WLP) of microbolometer vacuum package assemblies (VPAs).
2. Related Art
In commonly owned International Patent Application No. PCT/US2011/045600 filed Jul. 27, 2011, incorporated herein by reference, novel IR detectors, including microbolometer vacuum package assemblies (VPAs), are disclosed, together with methods for making them using wafer level packaging (WLP) techniques.
WLP methods and apparatuses for producing conventional semiconductor integrated circuit (IC) devices and microelectromechanical systems (MEMS) devices are known. Such techniques typically include the provision of a pair of complementary semiconductor wafers, within at least one of which has been fabricated a plurality of identical “active” devices. The two wafers are typically aligned in face-to-face abutment, bonded to each other, then cut or “singulated” into a plurality of individual devices.
In appropriate cases, WLP techniques can enable such devices to be produced reliably, efficiently and in a cost-effective manner. However, IR detectors have significantly different packaging requirements than, e.g., MEMS devices. For example, in MEMS devices, such as digital light projectors (DLPs) or inertial sensors, a greater emphasis is placed on non-corrosive environments having relatively poor “hermeticities,” i.e., sealing requirements, because they are predominately concerned with moisture permeation providing an electrolyte for corrosion. By contrast, IR detector devices, such as microbolometers (“bolometers” or “bolos”), require high levels of vacuum (e.g., low pressures) and associated hermeticity (e.g., low leak rate), and place a much greater emphasis on the degassing and subsequent outgassing rates of components, effected by high temperature vacuum baking or “bake out” regimens, prior to wafer bonding. Furthermore, the multiple sealing methods, which can be utilized by conventional MEMS production, are not an option for IR WLP manufacturing as, in some cases, the associated permeation rates cannot be tolerated, and in others, temperature limitations of the bolometer structures dictate very narrow windows of possible processing temperature options.
Accordingly, a need exists in the industry for WLP methods, systems, and apparatuses that accommodate these differences in packaging requirements so as to enable the volume production of reliable, efficient, and cost-effective IR detector and microbolometer VPAs.